Such spindles are used, in particular, in metal band rolling and treatment plants comprising, normally, various pieces of equipment, particularly for rolling, levelling, etching and other treatments. At the outlet of a section of the plant, the metal band must, generally, be wound into a coil to be then transported to another section or any other point of treatment.
To this end, a coiler is used which comprises a spindle consisting of a cylindrical bar brought into rotation around its axis and provided with means for fastening the end of the band which thus is wound into a coil around the cylindrical bar.
Generally, the winding bar is variable in diameter and may be retracted to enable retraction of the coil after winding.
To this end, the spindles used usually comprise a supporting shaft centered on an axis and associated with rotation driving means and a plurality of circular segments forming together a more or less cylindrical surface and attached to the central supporting shaft with the possibility of radial displacement in order to allow the variation of the diameter of the cylindrical surface thus constituted and on which the band is wound.
To control the diameter variation of the spindle, a rack-operated device is used conventionally, consisting of a control part, sliding axially on the central shaft, and on which at least one conical section is provided, working together with matching tilted faces, arranged in the segments, whereby the latter are maintained in a longitudinal direction with respect to the shaft and guided radially, in a transversal direction, in order to be able to come away from or to come closer to the central shaft by longitudinal displacement of the control part, under the action of an expansion rod mounted to slide in an axial bore of the central shaft.
The central shaft is generally mounted to rotate, via bearings spaced from one another, on a supporting chassis in which are located the rotation driving means. Displacement of the expansion rod can be controlled by a jack resting on the shaft, at the end opposite to the spindle.
For correct operation of the spindle; the different parts moving with respect to each other, must be able to do so with minimum friction. Careful lubrication at the level of the contact surfaces of the parts moving in relation to one another has been provided in this view.
Until now, such spindles had been used mainly in rolling plants. When the rolled band is hot, the internal parts of the spindle are heated up, which can disturb the operation of the spindle.
It has been, therefore, suggested to cool the spindle down by circulating a heat exchanger fluid, for example water, between the segments and the central shaft carrying the rack-operated control device. In such a case, however, it is necessary to ensure perfect tightness of the cooling system in order to avoid water ingress into the sections which must be lubricated.
The document GB-A-954015 describes, for instance, a spindle of this type in which each segment is provided, on its internal face, with ribs closed by the associated rack and in which the cooling fluid is forced to circulate. This fluid is introduced through the axial bore provided in the central shaft for the passage of the expansion rod and flows through orifices drilled radially in the shaft and each connected by a telescopic tube to a channel arranged on the rear section of each segment and to which the ribs of the former lead.
Such a layout does not enable to ensure perfect tightness and can only be used for moderate temperatures of the band and relatively short cycles, ranging between 3 and 5 minutes.
Besides, the fluid rejected under pressure at the front end of the spindle might be sprayed onto the band being wound, which is detrimental to the surface quality of the latter.
The purpose of the invention is to remedy these problems thanks to a new layout enabling to ensure very efficient cooling-down of the spindle and, consequently, winding around the said band whose temperature may be high.
Especially, for some time, researches have aimed at developing new technologies for continuous casting of bands of very little thickness and it is interesting, in such a case, to be able to wind into a coiler such a band around a spindle.
Yet, shortly after casting, the temperature of the band is still very high and, on the other hand, the winding time and, consequently, the time spent by the coiler on the spindle can be rather long, unless the coilers are kept very short, which would be of little interest.
Indeed, the winding time is related to the casting speed which is, obviously, much slower than a rolling speed.
It has therefore appeared that the spindles used until now, even if they are fitted with a cooling system, could not sustain such a heat transmission, because of the various thermal effects, particularly constraints and expansions of the various parts, liable to disturb the operation.
The invention enables to cancel these shortcomings thanks to provisions which, without complicating the construction of the spindle, ensure reliable operation of the said spindle, even in the case of low speed winding of very hot bands from, for instance, a continuous casting plant.